1. Field of the Invention
The present invention relates to a method of manufacturing a head suspension for a disk drive incorporated in an information processing unit such as a personal computer.
2. Description of the Related Art
A hard disk drive (HDD) used for an information processing unit has magnetic or magneto-optical disks to write and read data and a carriage. The carriage is turned around a spindle by a positioning motor. The carriage is disclosed in, for example, U.S. Pat. No. 4,167,765. This carriage has arms, a head suspension attached to each arm, and a head attached to the suspension and having a slider.
When each disk in the HDD is rotated at high speed, the slider slightly floats above the disk and air bearings are formed between the disk and the slider.
FIG. 1 shows a typical suspension 101 of an HDD. The suspension 101 has a load beam 103. The load beam 103 is fixed to a base plate 105 by, for example, laser welding. The base plate 105 is fitted to a carriage arm of the HDD.
The load beam 103 consists of a rigid part 107 of L1 in length and a resilient part 109 of L2 in length. A flexure 111 is fixed to the rigid part 107 by, for example, laser welding. An end of the flexure 111 has a tongue 113 to which a slider 115 is attached. The tongue 113 is pushed by a dimple 117, which is formed at an end of the rigid part 107. Although the dimple 117 is depicted with a solid line in FIG. 1, it is actually on the back of the tongue 113.
The rigid part 107 is provided with positioning holes 121 and 125, and the flexure 111 is provided with positioning holes 123 and 127.
The holes 121, 123, 125, and 127 are set on positioning pins of a jig to align the rigid part 107 and flexure 111 with each other, and the rigid part 107 and flexure 111 are fixed to each other by, for example, laser welding. The positioning and fixing of the flexure 111 to the rigid part 107 determine the vibration characteristics of the suspension 101.
Disks of recent HDDs are designed to densely record data and revolve at high speed. It is required, therefore, to provide a suspension of improved vibration characteristics to carry out precision positioning of a head on an HDD disk surface.
To meet the requirement, the suspension 101 must be compact. Namely, the distance A between the dimple 117 and a fitting center of the base plate 105 must be short. The distance A, however, must sufficiently be long to secure a proper distance between the holes 121 and 125 for correct positioning of the flexure 111 with respect to the rigid part 107.
If the distance A is excessively shortened to improve vibration characteristics, the holes 121 and 125 will be too close to each other, thereby deteriorating positioning accuracy.
To solve this problem, FIGS. 2A to 2C show a head suspension 101A for a disk drive according to a prior art. This prior art forms a positioning hole 125 on the side of a base plate 105. Even if the distance A (FIG. 1) between a dimple 117 and a fitting center of the base plate 105 is short, a sufficient distance is secured between positioning holes 121 (123) and 125 (127) for correct positioning of a flexure 111 to a rigid part 107.
Formation of the suspension 101A will be explained. FIG. 2A is a plan view showing parts of the suspension 101A before assembly, and FIG. 2B is a plan view showing the parts after assembly. In FIG. 2A, the flexure 111 is provided with the positioning holes 123 and 127. The base plate 105 is fitted to a reinforcing plate 129. The reinforcing plate 129 is solidly joined with the rigid part 107 of a load beam 103 through a bridge 131, to form a semi-finished suspension 133. The rigid part 107 is provided with the positioning hole 121, and the reinforcing plate 129 with the positioning hole 125.
A resilient material 135 is used to form a resilient part 109 of the load beam 103. The resilient material 135 is placed over the rigid part 107 and reinforcing plate 129 and is fixed thereto by, for example, laser welding. Thereafter, the base plate 105 is fitted to the reinforcing plate 129 and is fixed thereto by, for example, laser welding.
The semi-finished suspension 133 with the resilient material 135 and base plate 105 is set on a jig by passing pins of the jig through the holes 121 and 125, and the flexure 111 is laid thereon by passing the jig pins passed through the holes 121 and 125 through the holes 123 and 127, respectively. This precisely positions the flexure 111 with respect to the rigid part 107 as shown in FIG. 2B.
The distance between the holes 121 (123) and 125 (127) is appropriate for precision positioning between the rigid part 107 and the flexure 111. Under this state, the flexure 111 is fixed to the rigid part 107 by, for example, laser welding.
Thereafter, the bridge 131 is cut off by, for example, a press, to complete the suspension 101A of FIG. 2C.
One problem of this prior art is to leave the peripheries of the holes 125 and 127 on the base plate 105, to cause a horizontal imbalance on the base plate 105. This imbalance deteriorates the vibration characteristics of the suspension 101A.